You've got to delete old crap for new crap.
I have a nearly full bank of old gear, but I have less than a bag of quest items and I don't need space for more right now.
I get the impression that you guys aren't really into questing. Not trying to do quests definitely makes it easier to keep a clutter-free bank. I just don't understand why you'd design a game with quests that require all this bank space, and if you do multiple quests it requires multiple times the bank space, but the game is designed to limit your bank space for reasons I'm not clear on.